T-359 7–2Preparing Manifold Gauge/Hose Set For Use:If the manifold gauge/hose set is new or was exposed to the atmosphere, it will need to be evacuated to removecontaminants and air as follows:1. Back seat (turn counterclockwise) both field service couplings (Figure 7.2) and midseat both hand valves.2. Connect the yellow hose to a vacuum pump and refrigerant 134a cylinder.Figure 7.2 R-134a Manifold Gauge/Hose Set1. Manifold Gauge Set2. RED Refrigeration and/or Evacuation Hose (SAE J2196/R-134a)3. Hose Fitting (0.5-16 Acme)4. YELLOW Refrigeration and/or Evacuation Hose (SAE J2196/R-134a)5. Hose Fitting with O-ring (M14 x 1.5)6. High Side Field Service Coupling (Red Knob)7. BLUE Refrigeration and/or Evacuation Hose (SAE J2196/R-134a)8. Low Side Field Service Coupling (Blue Knob)- - - - -1. Evacuate to 10 inches of vacuum and then charge with R-134a to a slightly positive pressure of 0.1 kg/ cm 2(1.0 psig).2. Front seat both manifold gauge set valves and dis connect from cylinder. The gauge set is now ready for use.7.3 REFRIGERATION SYSTEM SERVICE-UNITS WITH STANDARD PIPING7.3.1 Service ConnectionsThe compressor suction, compressor discharge, and the liquid line service valves (see Figure 6-3) are providedwith a double seat and an access valve which en ables servicing of the compressor and refrigerant lines. Turningthe valve stem clockwise (all the way forward) will frontseat the valve to close off the line connection and open apath to the access valve. Turning the stem counterclockwise (all the way out) will backseat the valve to open theline connection and close off the path to the access valve.With the valve stem midway between frontseat and backseat, both of the service valve connections are open to theaccess valve path.For example, the valve stem is first fully backseated when connecting a manifold gauge to measure pressure.Then, the valve is opened 1/4 to 1/2 turn to measure the pressure.To High SideAccess ValveTo Low SideAccess Valve2133455 678
